1. Technical Field
The invention relates to photo masks and methods of fabricating semiconductor devices using such photomasks, and more particularly, to line photo masks and methods of fabricating semiconductor devices using the same.
2. Discussion of the Related Art
Generally, a semiconductor device includes individual elements and data line patterns electrically connecting these elements. The individual elements include a transistor, a capacitor and resistors, or the like. The data line patterns are disposed between the individual elements and function to transmit selected data of a user to the individual elements, and to display specific data to the user. Further, the data line patterns which are formed on a semiconductor substrate are greater in size than the individual elements but within the dimensional range which is allowed in the semiconductor fabrication processes. The configuration permits a device to minimize the resistance between lines during the transmission of data.
However, the narrower the tolerance range in the semiconductor fabrication process due to the reduction of design rules, the harder it is to form the requisite data line patterns on the semiconductor substrate. In the case of a semiconductor substrate having more than two data line patterns thereon, the effect of the semiconductor fabrication processes on the data line patterns should be carefully considered. For example, a photo process within the fabrication processes generates more light interference to images transmitted onto a photoresist layer in an exposure operation when more than two data line patterns are to be formed on a semiconductor substrate as compared to employing one data line pattern. The light interference can have an adverse effect on the integration of the data line patterns on the semiconductor substrate and on the uniformity of the distances between them. Thus, it is necessary to employ a method which overcomes the light interference effect and is within a given design rule. Thus, the data line patterns must be formed on the semiconductor substrate without electric shorts or cutting of the data lines.
U.S. Pat. No. 5,807,649 to Lars W. Liebmann, et al (the '649 patent) discloses lithographic patterning method and a mask set therefor which employs a light field trim mask. According to the '649 patent, the method uses the mask set including forming a device layer in a photosensitive layer using a phase shift mask and a trim mask. The phase shift mask has a first opaque region which forms a device layer and a first transparent region defining the region. The trim mask has a second opaque region for masking the first opaque region of the phase shift mask from light, and a second transparent region for defining the region. Thus, the phase shift mask and the trim mask can provide a specific device layer.
However, the method of the '649 patent needs to perform two distinct photo processes related to two photo masks, thereby causing the increase in production time and costs. Further, since one of the two photo masks is a phase shift mask, a process of forming the phase shift mask is more complicated than a process of forming a binary mask. Again, this results in increasing the production time and costs of producing the photo mask.